1. Field of the Invention
This invention relates to a light-intercepting device in a single-lens-reflex camera having a focal plane shutter, and is more particularly directed to a device for preventing incoming light from passing through the clearance between the camera body and the shutter curtain to strike the camera film.
2. Description of the Prior Art
In single-lens-reflex cameras having a focal plane shutter, clearance is provided between the shutter curtain and the camera body to allow the shutter to move freely. When a camera having such construction is used in bright light, oblique light rays passed through the lens are reflected within the light-transmitting frame of the camera body and may pass through the clearance to strike the film in the camera when the shutter is in closed position, causing the surface of the photographic film to be fogged. This problem is particularly evident when camera lens interchange is effected in direct sunlight.
A first prior art proposal for overcoming this problem has been to attach a light-intercepting material, such as Telemp, to the camera body within the clearance space or to the outer surface of the mirror box with the material being urged against the shutter curtain. However, the engagement of the material with the shutter curtain substantially increases the frictional resistance to movement of the shutter curtain, which in turn has caused the velocity of the shutter curtain to be reduced and also to be somewhat irregular. A second prior art proposal has been to support light-intercepting members of flexible and opaque thin films such that pocket-like or deformed cylindrical bulges in the films are urged against the surfaces of the shutter curtain at the upper and lower portions thereof, thereby reducing frictional drag on the shutter curtain.
Both of these prior art proposals are unsatisfactory because they involve complicated configurations which result in poor manufacturing efficiency. Moreover, in the first proposal, the flapping of the shutter curtain which occurs during shutter movement prevents close contact from being maintained between the shutter curtain and the light-intercepting material, thereby reducing the light-intercepting effect. With respect to the second proposal, in order to reduce the frictional drag on the shutter curtain, the deformed cylindrical shape of the light-intercepting members requires that the area of contact be reduced. To compensate for the resulting reduction in the light-intercepting effect, the light-intercepting members would have to be brought into considerably stronger surface contact with the shutter curtain in order to provide complete light interception. Moreover, the degree of contact of such members with the surfaces of the convexo-concave shutter curtain is low.
In accordance with a third prior art proposal, the front and rear surfaces of the shutter curtain at the upper and lower edges thereof are held by and between light-intercepting members which comprise opaque rubber-coated films which are bent into a V-shape having an angle of 120.degree. or 140.degree., for example. One leg of each bent film is fixedly secured to the mirror box or to the camera body in a position such that the end of the other leg of the film is urged against the shutter curtain. The light-intercepting members make contact with the shutter curtain only by virtue of their being bent and therefore lack sufficient positive force for bearing against the shutter curtain. As a result, the light-intercepting members tend to be forced back by the shutter curtain and thus fail to provide close contact with the shutter curtain. Furthermore, light-intercepting members of this type have poor durability, because the force with which the film bears against the shutter curtain decreases with use.